Archive for the ‘In the field’ Category

We have come back to this key area of Antarctica because it is on the ‘front line’ of how the continent is responding to warmer air and changing wind patterns. The Larsen B ice shelf, larger than Delaware in the 1990s, disintegrated in a matter of weeks in 2002. Between Jan 31 and March 17 of that year, 3250 km2 of ice 220 meters thick (over 700 feet) crumbled away after a very warm summer with extensive melting. However, one area of the Larsen B remained intact: a sheltered southern bay called Scar Inlet. In the past 14 years, this remnant shelf has changed dramatically, developing many new rifts and fractures. Moreover, since late 2011, the larger bay where the Larsen B once resided has been covered with a solid sheet of frozen ocean ice, called ‘fast ice’ because it is ‘fastened’ (frozen) to the coastline. We suspect that now this fast ice is supporting the weakened Scar Inlet shelf, and that the shelf is poised to break-up (at least partially) if the thin fast ice breaks away. This generally happens in late austral summer. Our mission is to set up a series of instruments for a few weeks to measure the structural state of both the fast ice and the Scar Inlet ice shelf plate.

The two color images are from NASA’s MODIS sensor, and record ‘before’ and ‘after’ conditions of the Larsen B ice shelf disintegration of 2002. The blue specks on the January 31st image are melt ponds from warm summer conditions. In the March 7 image, the blue areas are disintegrated ice blocks, often flipped on their side in the dynamic break-up event. The three images at the lower left record how the surface lakes disappeared over the weeks leading up to the break-up. At top right is a Landsat 7 image showing the melt ponds in more detail in a preceding summer. Image credit: T. Scambos, Scambos et al., 2003 AGU Antarctic Research Series v.79.

The images above are from satellite data taken during the break-up of the Larsen B in 2002. You can see why we are going at this time of year – this is exactly the part of the year, late summer, when these kinds of rapid break-ups can occur. The key factor is summer melting – in years when the shelf ice is covered with small blue melt ponds, there is a strong likelihood of disintegration. The lakes accelerate fracturing in the ice by filling cracks with water and breaking them open, a process called ‘hydrofracture’.

The remnant Scar Inlet ice shelf has remained intact but has evolved considerably in the years since 2002, developing new rifts, a more fractured margin, and deep troughs near the ice front. Below is a series of images showing how the ice has evolved, and the recent persistent fast ice.

The research team has spent the past few years installing sensors on the ice shelf and on the rocks nearby. We’ve talked about these in the OTI blog before – the “AMIGOS” stations, having cameras, a GPS, and weather and ice-measurement instruments, and the continuous precision GPS stations, which also measure weather as well as ice or rock motion down to millimeter precision. The station on Cape Disappointment has been very useful (not disappointing at all!) for tracking how the edge of the ice shelf has crumbled over the past few years and mixed with the sea ice. A recent set of pictures – a panorama – is shown below.

Looking south from the Cape Disappointment AMIGOS station toward the Scar Inlet Shelf on January 2, 2016. The near foreground is the rocky cape where the AMIGOS system is installed; just beyond that is a part of the ice front that has fractured and retreated slightly over the past five years. In the distance is the remainder of the Scar Inlet ice shelf and the mountains of the Antarctic Peninsula. The entire ice surface in view is at risk of more rapid break-up if warm summer conditions occur.

A new satellite tool is now available for tracking how the Scar Inlet region evolves. Landsat 8, launched in February of 2013, provides 15m resolution images of the world’s land and ice cover, with color channels at 30 m resolution and thermal data as well. A false color image (using near-infrared light for red, red light for green, and green light for blue, to create an image that enhances the ability to detect melting) is shown from January 6. The fast ice has partially flooded due to warm conditions in late December and early January, and there are several cracks in the ice. A few ponds appear on the ice shelf and adjacent glaciers.

Our plan is to visit several of the stations, and install additional GPS stations (from the air – that should be interesting…) and then bring our additional cameras and other instruments to Cape Disappointment to record ~2 to 3 weeks of summer conditions on the fast ice and ice shelf in detail. Stay tuned…..

Landsat 8 image from January 6, 2016, showing summer conditions on the fast ice, glaciers, and ice shelf in the study area. .

Following the Night of the Tormentas, we ended up spending three more nights there, punctuated by sweltering days, humid nights, occasional storms, numerous power outages, and even losses of running water. We were hopeful that each day would be our last, and even got as far as turning in our linen one morning only to hear that there were continuing problems with getting our C-130 tested. Following that disappointment, we were issued new linens and were thrilled to see the plane takeoff and make four circuits around the base.

We were then told to have our new linens checked in and have our bags ready for pickup at 8:00 a.m. the next morning. We had our usual beers at La Fortunata that afternoon, followed by our first and only off-base dinner at Zarco, an Italian place.

Last Dinner Off Base at Zarco, an Italian Restaurant

The next morning went off more or less as planned, and we took off at about 10:00 a.m. for Ushuaia, about five hours south of El Palomar. There we dropped off half our passengers who were bound for Argentine bases other than Marambio, while we took a few photos of the surrounding sunlit mountains and glaciers, huddling behind a wall to shield ourselves from a chilly 30 knot breeze, and waiting for our C-130 to be refueled.

On Board the C-130 Flying to Ushuaia

The C-130 Being Refueled

Thirty minutes later we were again airborne, this time heading for rainy Rio Gallegos. IAA maintains a very nice barracks area there (Rio Gallegos is another Fuerza Aerea base). We were served two meals, pasta and beef at about 4:00 p.m., and polenta and beef at about 9:00 p.m. Some of us read books, while the others watched “Battleship,” a US Navy recruiting film in English with Spanish subtitles disguised as a science fiction thriller. Spoiler alert: the Earthlings win.

Rio Gallegos DNA Building

Rio Gallegos Mess Hall

The next morning we awoke to a cloud-free sky above a landscape reminiscent of eastern Colorado. We watched from the passenger terminal as our cargo was reloaded, and then stepped aboard the C-130 for the final leg of our now 14-day journey south. After an uneventful four hour flight, we touched down in Marambio.

Terry Watching from the Passenger Terminal as the Cargo Is Reloaded

Rob Watching from the Passenger Terminal as the Cargo Is Reloaded

C-130 Cargo Plane being Reloaded in Rio Gallegos

Boarding the C-130 for the Final Leg of Our 14-Day Journey South

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Our move to the west side of the Peninsula renewed the challenges we have faced before in trying to get work done over the high, narrow Antarctic Peninsula ridge. The weather is rarely good on both sides at the same time, and communication can be more difficult. Iridium satellite phones or a powerful shortwave radio are needed. We have the Iridium system, which can be erratic when used across international Iridium numbers. And now, in early May, daylight lasts a mere seven hours.

The sea off the Antarctic Peninsula. Daylight is now down to seven hours in this part of the world. (Credit: Ted Scambos, NSIDC)

Days passed with more or less the same appearance outside: dimly lit low clouds, often with snow flurries. In the week ending April and opening May, we tried three times to high-jump over the icy wall of the Antarctic Peninsula, aiming to revisit the first site we had scouted last month, namely the rocky overlook near Crane Glacier—perfect for our instrumentation. But we succeeded only once, and even then the helicopters found the outcrop covered in deep snow, hiding the many large boulders covering the site and making it impossible to land. It was time to head north. It looked like we would get nothing installed.

But on our path to the South Korean research station (King Sejong Station, on King George Island) lay one more worthy target—Cayley Glacier and the adjacent outcrop called Spring Point. Cayley Glacier is one of the largest west-flowing glaciers in the northern Antarctic Peninsula, and it has been thinning significantly in recent years. It represents a vantage point to observe the changes in western AP glaciers up close, and make some long-range measurements of changes driven mostly by the more recent and more dramatic changes on the eastern side. The ship sailed northward along the coast overnight, setting us up for a few hours at our last best place to measure climate change in the Antarctic Peninsula.

Next morning was snowy and gray, but still majestic with icy hills framing the large calving front of the Cayley. After some preparations, we boarded Zodiac watercraft (an inflatable landing craft fitted with outboard motors) and nine of us motored over to the Spring Point promontory. We loaded the Zodiac with a seismic monitoring station and an automated camera.

You Dong Cho directs the helicopter to a landing area near our Spring Point instrument installations. (Credit: Ted Scambos, NSIDC)

We could only man-haul some of the gear from the shoreline up the rocky hillside—the easy way to do it would be an airlift by the helicopters. But the weather was miserable—drizzle and snow, fog and low cloud. We were unsure if they could possibly manage it. From the hilltop we watched the back deck of the Araon, waiting to see if the cargo load would leave the deck by air (or we would have an arduous time with ropes and pulleys from the shore, requiring hours).

Despite the raw conditions, the pilots pushed on, doing three quick loads setting everything within 20 yards of our installation sites. A few hours of rock-bolting and assembling, and we had our site: three important instruments for monitoring change. The seismometer would record the fracturing and calving of the ice in the nearby glacier (about 2 miles away) as well as other glaciers up and down the Peninsula; the camera would witness the local calvings and the changes in the ice front; and a GPS system (installed earlier, but upgraded during our visit) would measure the rebound of the Earth as the great mass of ice slowly flowed off of the Antarctic continent.

Amy Leventer of Colgate College and Ronald Ross install an Extreme Ice Survey camera at Spring Point overlooking the Cayley Glacier calving front to the east, with the R/V Araon in the foreground. (Credit: Ted Scambos, NSIDC)

Ted, Amy, and Ronald make final camera adjustments as bergy bits float by in Brialmont Cove in Hughes Bay. (Credit: Erin Pettit, University of Alaska Fairbanks)

We finally got ‘er done. Even better, that night was the planned End-of-the-Cruise dinner party—a huge variety of good food, sweet rice wine, beers, and very good company. We are now heading north to King Sejong station.

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After returning from the day trip to the Crane Overlook site on April 17, we received satellite images that completely changed our plan. The images from both a NASA and a Canadian satellite showed that persistent westerly winds starting in early April had opened a large gap in the sea ice just to the east of the Larsen A, B, and C—a long highway of dark water that we could use to get to areas we have been trying to reach for four years. But the opened road on the eastern Peninsula came with a significant risk: at this point in the Antarctic season, such a path could freeze over or slam shut in a matter of days, making it difficult even for a powerful icebreaker like the Araon to escape.

The KOPRI (Korean Polar Research Institute) scientists were willing to take the risk, in part because the ship is fairly fast, capable of up to 14 knots, and because the science potential was high. The weather is much drier on the leeward eastern side of the Antarctic Peninsula, so we would be likely to fly more often. Communications and weather safety are better because one can see conditions approaching the ship or the field site from a long distance (without the blocking of the high Antarctic Peninsula ridge).

That evening, we took the ship as fast as possible over the northern tip of the Peninsula to the eastern side and sailed down into the gap less than two days later.

The flock toboggans away from the sound of the passing ship.(Credit: Ted Scambos, NSIDC)

And there we were: at the fast ice edge of the Larsen B Ice Shelf, ready to fly with helicopters to the three major glaciers of our study area, one of them already fast-moving and thinning as a result of global warming (Crane Glacier), and two others (Flask and Leppard glaciers) that were poised to change if the last remnant of the Larsen B, the Scar Inlet Ice Shelf, collapsed.

Rifts near the calving front of Scar Inlet Ice Shelf could eventually form tabular icebergs. (Credit: Ted Scambos, NSIDC)

The next day (April 20) was clear and warm. The forecast suggested a gradual shift to cooler southern winds by late in the day. We loaded the helos according to a complex plan, trying to get as much done as possible. We would identify a second rock outcrop and install a seismic monitoring station, and begin work on a multi-instrument AMIGOS site on a small crevasse-free section of lower Leppard just a few miles away from the seismic site.

The flight to Leppard was spectacular and revealing. The remnant Scar Inlet shelf from the once-vast Larsen B is now completely fragmented, as cracked as a windshield after an accident, with huge deep rifts indicating fractures on the underside of the floating ice as well. It is clear that the next warm summer will be the last one for this shelf. We were eager to get to our site and get going.

Closely spaced crevasses on Scar Inlet Ice Shelf could fill with melt water during the next warm summer, leading to a possible disintegration event as happened to the main Larsen B in 2002. (Credit: Ted Scambos, NSIDC)

But there were problems. Our search on the mountain next to Leppard Glacier for a good seismic mounting site was hampered by bumpy winds around the peaks. Lower down, the rock sites were covered in gravel and loose talus, and were not suitable. So we decided to put the seismic station on the glacier at the AMIGOS site. Problems with the Iridium satellite phones arose. We could not contact the ship, except using the helicopter radios, and they had to be aloft to make a clear call.

Ted Scambos records some notes on Leppard Glacier. The field instrument next to Ted is a backpack-mounted, gas-powered steam drill.(Credit: Jennifer Bohlander, NSIDC)

Slowly things moved along despite these obstacles. We conducted a radar survey, skiing a few km across the glacier. The seismic crew began to build the station. A Korean geologist and I returned to the ship in early afternoon. On the flight back, I noticed low fog forming over the Scar, a very ominous sign. Fog had trapped a group of us for over a week in 2010, and that was in summery January, not April. When we landed I asked the pilots to hurry back and get the rest of the crew right away.

An approaching fog bank was the precursor to an intense snow squall that forced a retreat from Leppard Glacier by the remaining field team of seven scientists. (Credit: Ted Scambos, NSIDC)

But after the helos left, we realized that fog was only the beginning of the weather change. Far from being a gradual wind shift, a sudden abrupt blast of south wind hit the ship, and within minutes we were engulfed in cold blowing snow and mist. Temperatures plummeted. Our sunny day was going to end with a powerful snow squall, with seven scientists still at the Leppard site. Conditions remained beautiful there, 70 miles away.

The Araon, enshrouded in freezing mist and battling 40 knot winds at the Larsen B fast ice edge, awaits the final helicopter returning with a field party from Leppard Glacier. (Credit: Erin Pettit, University of Alaska Fairbanks)

We radioed the pilots and told them about the declining conditions at the ship, and they loaded the passengers and headed back. By the time they arrived at the ship, a gale of 40 knots was blowing, and visibility was only a mile or so. The pilots made two amazing landings in the blustery winds, with all passengers and gear safely returned.

By nightfall, winds had risen to 60 knots out of the south, with temperatures near zero degrees Fahrenheit. The scientists and ships crew realized that these were exactly the worst conditions for keeping the narrow lane of ocean clear of ice. Cold winds would freeze the open water, and the pack to the east of us (full of thick older ice) would start to shift westward and close us in. The Araon put on all speed and glided through the gathering slushy ice, a gale at its back, until we were north of Robertson Island (the most likely ‘pinch point’ for the drifting ice to close us in).

We were not done though—as the first gale subsided the next day, we returned south again, finding that the road was narrow but not completely shut. We traveled past the Larsen B into the Larsen C, almost touching the Antarctic Circle (in late April!) and collected a core from a key site of the Larsen C. On our way north again, we launched a quick mission to recover gear that had to be left behind when the squall hit. Then we left for good, as the oncoming Antarctic winter was rapidly freezing the sea around us.

We now are again on the west side, in a fjord called Flandres Bay, just opposite our main instrument sites, with one more week to get some stations installed.

Tomorrow looks like flyable weather.

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After preparations in Punta Arenas, including shopping for comfort food (cheese, bread, peanuts, breakfast cereal) that we thought we might not see for a while, the LARISSA glaciology team boarded the Araon, South Korea’s new polar research vessel. The Araon is a large ship, and very clean—it was commissioned in 2010. I noticed something right away walking through it—a new icebreaker smell, a bit like a new car. The labs and especially the cabins are quite spacious, and very comfortable.

The R/V Araon at the quay in Punta Arenas. (Credit: Ted Scambos, NSIDC)

The bridge of the Araon. (Credit: Ted Scambos, NSIDC)

A cabin on the Araon. (Credit: Ted Scambos, NSIDC)

With a late party on the night before departing (April 10), we boarded the Araon on the 11th and sailed out the Straits of Magellan, eastward, and then south. One of the first things we did was listen to a safety briefing video introducing us to the ship’s systems. At the end, the announcer told us that the Araon was “the ship of dreams for polar research,” and we had to agree. It was large, powerful, well-equipped, and new.

The food on board is indeed Korean, although on some occasions they have treated us to some western favorites: spaghetti, pan-grilled steak, eggs and bacon for breakfast. But in fact the best treats have been the Korean-style sushi and Korean barbecue: thawed fresh-frozen fish or grilled pork with lettuce leaves and rice and wasabi. And the soups have been very good; different, but very good. The chicken soup had a kind of dumpling made from rice paste, very soft and white and it had absorbed the taste of the stock very nicely. They allow a little beer or wine with dinner about every other night. Life is good; oriental, but good.

Sailing across the Drake Passage south of Cape Horn, we made very good speed, and the ocean was not very rough. We spent the time preparing the equipment: the K-AMIGOS systems (similar, but newer and upgraded versions of the AMIGOS systems we installed in previous years), and the “Balog Cameras” as we called them, for the project by James Balog known as The Extreme Ice Survey.

Jenn, Ronald, and Ted work on the Balog Camera. (Credit: Ted Scambos, NSIDC)

Ronald, Rob, and Ted work on the Balog Camera. (Credit: Ted Scambos NSIDC)

Ted and Erin Pettit, glaciologist at University of Alaska, Fairbanks, with a backdrop of the peaks and glaciers ringing Beascochea Bay. (Credit: Ted Scambos, NSIDC)

By the morning of the 15th we were off the western coast of the Antarctic Peninsula at 65 degrees South in Beascochea Bay, just above the Antarctic Circle. This was the best location for flights to our target locations for instruments, all on the eastern side of the Peninsula. But it meant flying over the ridge of the Peninsula, a tricky thing both for the weather and for the helicopters (lots of climbing and shifting winds).

Still, we’re set, with a huge and capable ship, instruments ready to go, and plenty of things to do while waiting for a good weather window in the fjords of the Antarctic Peninsula.

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Thu 12/20: Got on board the Dash-7 around 9:00 a.m. together with outgoing field operations manager Andy Barker, field assistant Roger Stilwell, scientists Beth Davies, Mike Hambrey, and Daniel Farinotti, and the flight crew of pilot Phillipe Leblanc and mechanic Chad Jones. We landed in Punta Arenas around four hours later. We were all staying at the Diego de Almagro hotel so we all piled into a van from the British Antarctic Survey (BAS) contractor AGUNSA. Later that afternoon, we all visited station support assistant Neil Malcolm who had injured his back skiing a couple of weeks earlier, and was making a fantastic recovery at a local hospital. Made a quick visit to the DAMCO warehouse to check on batteries. That evening I joined the other Dash-7 passengers for a fine dinner at La Marmita as they were all flying out of Punta Arenas early the next morning.

Fri 12/21: Went over to the DAMCO warehouse and, with the help of a couple of AGUNSA workers, located the two batteries in the AGUNSA warehouse that I had tried to give Chris Hill of the Lake Ellsworth drilling project that he was unable to use. Added these two to the other six we had found in the DAMCO warehouse back in October. Arranged with Dave Morehouse to have these eight batteries sent to Tamsin Gray in Rothera on the next Gould cruise to back fill the five she had given me, plus to pay back Rothera for the other materials (poles, brackets, etc.) I had acquired during my stay.

Sat 12/22: Logged into AMIGOS-6 from the hotel, updated some program files, and downloaded the first two Sony images of the work crew. Posted the Sony images and sent an email to Ash Fusiarski pointing him to the images. Checked out of the hotel and walked over to the DAMCO warehouse. Met the DAMCO liason Marcella, loaded my gear into the DAMCO van, was driven to the airport, and was assisted by Marcella through the baggage check-in procedure including the payment of excess baggage charges. The flight to Santiago with a short stop in Puerto Montt was uneventful, as was the 4-hour layover in Santiago. I boarded my flight to Dallas at 10:30 p.m.

The first Sony camera images of the repair team (minus Terry) captured by AMIGOS-6. Left to right: Phil Harle, Jim Scott, Ash Fusiarski, Ian (Cheese) Rudkin, and Al Howland.

Sun 12/23: The ten-hour flight from Santiago to Dallas was also uneventful. Made it through customs ok and even had time for some breakfast. Flew on to Denver arriving at 9:45 a.m., and just made it to the 10:25 a.m. bus to Boulder. My son Alex picked me up at the Table Mesa Park-n-Ride and, after a quick visit with my wife Sue at home, I dropped off my equipment at NSIDC. Ted was at work (of course) and he congratulated me on a successful field season.

Mon 12/24: Sometime between 2012/12/23 2000 UTC and 2012/12/24 1200 UTC, a 1000-foot iceberg calved off the ice shelf about 2 miles from AMIGOS-6 on Cape Disappointment.

The right side of these AMIGOS-6 images show a 1000-foot iceberg calving off the ice shelf 2 miles southwest of the AMIGOS-6 tower. The event occurred between the time the second and third images were acquired. The earlier first image and later fourth image are included because they have better illumination.

Zoomed-in version of a Landsat-derived map of LARISSA field sites on the Larsen B Ice Shelf. The map shows all the AMIGOS (blue asterisks) and cGPS (red circle and black square) sites visited by Terry Haran in November and December 2012. Cape Disappointment is shown but doesn’t have a blue asterisk, and AMIGOS-6 is located on the small black outcrop just below and to the left of the black circle. Colors indicate ocean depths derived from sonar data: red for shallow areas and blue for deep areas. For scale, Flask Glacier is about 4 miles across at the location of the AMIGOS-3 blue asterisk. (Courtesy Eugene Domack and Caroline Lavoie, Hamilton College)

Both the 0900 and 1100 UTC AMIGOS images from Flask Glacier and Scar Inlet showed good contrast at both sites, and satellite images looked good as well. We took off at 9:32 a.m with six people on board: pilot Al Howland, myself, field assistants Ian (Cheese) Rudkin and Ash Fusiarski (who spent the entire previous day with Daniel Farinotti man-hauling radar equipment on Flask Glacier), and builders Jim Scott and Phil Harle. Got lots of good pictures on the way to Cape Disappointment, particularly of the shear zone running along the northwestern side of Scar Inlet.

Ice-capped Bildad Peak at an elevation of 2,600 feet rises some 1,300 feet above Flask Glacier and is visible in some AMIGOS-3 images. View is toward the northwest.

The northwest edge of Scar Inlet ice shelf, the last remnant of the Larsen B Ice Shelf, is being ripped open due to the increasingly large difference in velocity between slower moving ice northwest of the shear margin, and faster moving ice to the southeast emanating from Flask Glacier

Shear zone middle

Shear zone south

The collapsed AMIGOS-6 tower (middle, left) as seen during one of three passes made over Cape Disappointment just before landing.

After three passes around Cape Disappointment, including two touch-and-go landings, Al set us down at 11:14, about a mile northwest of the AMIGOS-6 site.

The team gathers materials and then rope up in anticipation of hiking out about a mile to the AMIGOS-6 site. (Courtesy Jim Scott, British Atlantic Survey)

Field assistant Cheese Rudkin at the toppled AMIGOS-6 tower on Cape Disappointment.

Seals (probably Weddell) resting on the banks of a sea ice lead extending south from Cape Disappointment. (Courtesy of Jim Scott, BAS)

We donned crampons and harnesses, roped up, split into two groups of three, led by Cheese and Ash each pulling a sled full of equipment, and left the plane at noon. Cheese, myself, and Al arrived at AMIGOS-6 at 12:50, followed closely by Ash, Phil, and Jim. Al, who used to work as a “rigger,” led the group raising the tower, installing the new three-pole outrigger arrangement, and securing the poles to the wire basket rock anchors.

Phil and Ash work on attaching the AMIGOS-6 electronics and high resolution camera enclosure to the now erect and pole-strengthened tower. (Courtesy Jim Scott, BAS)

The upwind anchor which had failed was rebuilt, and strengthened with an additional new wire basket rock anchor. The rock anchor surrounding the tower, which also had failed, was disassembled but not rebuilt. The consensus was that installation of the new poles and strapping the battery box to the tower were providing a sufficient tower anchor. Jim Scott rewired the solar power input and 12-volt output lines to the solar charger assembly, while I added a fourth battery to the battery box and tested the system.

Terry talks to Ted Scambos at NSIDC in Boulder to verify that at least some valid data are being received, so the Iridium cable and antenna seem to be working correctly. (Courtesy of Jim Scott, BAS)

I was dismayed that AMIGOS-6 wasn’t connecting to the internet through the NSIDC FTP server — until I remembered that I had seen an email a couple of days earlier indicating that the server and its associated disks would be down for maintenance all day on December 19. I called Ted who verified that, but who then suggested that he would ask the system administrators if FTP could be brought back up for my test. We started packing up, I called Ted back who said the FTP server was back up, and I then verified that AMIGOS-6 was connecting correctly. We were also able to verify that weather and GPS data were being received via email correctly, but we were unable to verify that images were being correctly received since the FTP disks were still down.

But since all this had been working correctly in Rothera, albeit with a different Iridium cable and antenna, we felt that it the system was working okay. We started walking back to the plane at 4:30 p.m., arrived at 5:00 p.m., and took off for Leppard Glacier at 5:30 p.m.

After taking off from Cape Disappointment, a final view of the now repaired AMIGOS-6 tower.

After taking off from Cape Disappointment at 5:30 p.m., and before proceeding to Leppard Glacier, we made a slight diversion over Exasperation Inlet and part way up Crane Glacier. Ted Scambos wanted us to obtain some aerial photos of the lower part of the glacier which we did.

Composite image of Exasperation Inlet from Exasperation Point. Cape Fairweather is on the left. Crane Glacier enters the inlet far to the left and out of the frame. The foreground view is entirely sea ice, at most a few meters thick. There are a few icebergs in the foreground and many more as we approached the glaciers from which most of the visible icebergs have been calving. Prior to the disintegration event in February 2002, the entire foreground view of this image would have been of the Larsen B Ice Shelf which was several hundred meters thick.

The calving front of Mapple Glacier. Crane Glacier enters Exasperation Inletfar to the right of this image.

The calving front of Crane Glacier is at the far left of the image and Exasperation Point is at the far right. The flat large tabular iceberg in the foreground has probably drifted into Exasperation Inlet from a glacier far to the south.

The 2.5-mile wide Crane Glacier calving front is heavily crevassed. The crevasses appear to extend to great depth causing virtually all icebergs that calve off to be very narrow relative to their total thickness. Such icebergs cannot float upright, and so either they immediately lay down on their side or they crumble into bergy bits. Thus most of the horizontal surfaces of the large flat icebergs in this image were originally the vertical surfaces of crevasses in the the glacier before calving.

Composite image of the northern side of the Crane Glacier calving front and the iceberg melange just downstream. The calving front is about 150 feet high and the largest icebergs are over 1,000 feet across. The Crane Glacier surface has lowered by several hundred feet since 2002. A small terrace of stranded glacial ice just above where the calving front meets the rock wall stands about 500 feet above the surface of the melange.

A side glacier about 2 miles across flows into Crane Glacier about 9 miles upstream of the calving front. A relatively uncrevassed area on the surface of Crane is visible in the lower left corner of the image and may suitable for some future instrument installation via Twin Otter.

About 20 minutes after taking off, Al announced it was time to exit Crane and head over to Leppard. We flew over the upper reaches of Mapple, Melville, Pequod, and Starbuck Glaciers, and crossed Flask Glacier just upstream of the AMIGOS-3 site where Ash and Daniel had been collecting radar data just the day before.

A panorama taken where we exited Crane Glacier fjord en route to Leppard Glacier. A pressure ridge marks the confluence of the left (southwest) and right (west) branches of Crane Glacier. Another side glacier can be seen entering the fjord from the right (northwest).

Bildad Peak and Flask Glacier, this time looking southeast. AMIGOS-3, though not visible here, is located near the right edge of the image.

Panorama of Flask Glacier from Spermwhale Ridge on the left to Pip Cliffs on the right.

Due west view looking up Flask Glacier which is almost 3 miles wide atthis point.

Another five minutes brought us within sight of the LPRD cGPS on Leppard Glacier. We made a touch-and-go landing, and then a final landing at 6:15 p.m.

Images of the Leppard Glacier continuous GPS system before and aftera touch-and-go landing

The goal at this site was to simply raise the solar panels. This required first re-excavating the hole dug during our previous visit three weeks earlier. Then more snow and ice covering the two solar panel poles below the floor of the hole needed to be chipped away so that the overlapped section of pole extension installed two years earlier could be fully exposed. Then the now useless guy wires extending to the deadman snow anchors needed to be cut, the clamps binding the extension needed to be loosened, the extension slid up about three feet, and the clamps re-tightened.

Images of the Leppard Glacier continuous GPS system before and afterbeing raised about 3 feet.

All this was done as planned, but unfortunately the cable to the weather station was accidentally damaged in the process. However Ash Fusiarski was able to repair the damaged cable, and Seth White of UNAVCO in Boulder was able to verify that the system was posting good GPS data, although confirmation from Seth of the posting of good weather data had to wait until the next day.

Ash Fusiarski repairing the damaged weather station cable after the solar panels had been raised.

We finished the repairs and took off for Rothera at 8:15 p.m. arriving at 9:30 p.m. After scarfing down the dinners that had been saved for us, I bought a round of beer in the bar for the entire crew. I didn’t go to bed that night since I had to unpack all our gear, separate out the BAS gear that needed to stay in Rothera, and then repack all my gear for the Dash-7 flight in the morning.